This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This collaboration with Dr. Mehmet Toner of the BioMEMS Center at Harvard University (a P41 Resource) is focused on applying microfabrication techniques to the development of a high-throughput large particle sorter in R&D Project 2. We are investigating passive particle manipulation within microfluidic channels. Using a variety of specific channel orientations, the BioMEMS Center has been able to show particle focusing, periodic particle spacing, and parallel streamlines with no external fields. We are investigating the use of this technology to focus particles in the 100-micron diameter range. We expect this approach to easily scale to this dimension and fabrication of multiple focusing channels on a single substrate should be straight- forward. As such we have obtained a few sample chips and analyzed focused particles in a simple fluorescence analysis device, with some success. The advantages of this approach include robustness, reproducible operation and no need for any external particle manipulation field.